System.Data.SqlClient.SqlException: 'Incorrect syntax near ','.'

Question

I am trying to make a simple app that gets your IP address and stores it in a sql database 1
But I am getting a error saying

System.Data.SqlClient.SqlException: 'Incorrect syntax near ','.'

Here is my code:

using System;  
using System.IO;  
using System.Net;  
using System.Net.Sockets;  
using System.Data.SqlTypes;  
using System.Data.SqlClient;  
using System.Text;  
  
namespace Test  
{  
    public class GetIP  
    {  
        public static string GetIPAddress()  
        {  
            string content = File.ReadAllText(@"C:\Users\Home\source\repos\Test\Test\IP.txt");  
            string IPAddress = string.Empty;  
            IPHostEntry Host = default(IPHostEntry);  
            string Hostname = null;  
            Hostname = System.Environment.MachineName;  
            Host = Dns.GetHostEntry(Hostname);  
            bool infile;  
            foreach (IPAddress IP in Host.AddressList)  
            {  
                if (IP.AddressFamily == AddressFamily.InterNetwork)  
                {  
                    IPAddress = Convert.ToString(IP);  
                }  
            }  
            if (content.Contains(IPAddress) == false)  
            {  
                var datasource = @"(localdb)\MSSQLLocalDB";//your server  
                var database = "IP"; //your database name  
  
                //your connection string   
                string connString = @"Data Source=" + datasource + ";Initial Catalog="  
                            + database + ";Persist Security Info=True;User ID=";  
  
                //create instanace of database connection  
                SqlConnection conn = new SqlConnection(connString);  
  
                //create a new SQL Query using StringBuilder  
                StringBuilder strBuilder = new StringBuilder();  
                strBuilder.Append("INSERT INTO IP (IP) VALUES ");  
                strBuilder.Append($@"(N'{IPAddress}', ");  
                conn.Open();  
                string sqlQuery = strBuilder.ToString();  
                using (SqlCommand command = new SqlCommand(sqlQuery, conn)) //pass SQL query created above and connection  
                {  
                    command.ExecuteNonQuery(); //execute the Query  
                    Console.WriteLine("Query Executed.");  
                }  
                strBuilder.Clear(); // clear all the string  
  
                  
                strBuilder.Append($"UPDATE IP SET IP = N'{IPAddress}'");  
                using (SqlCommand command = new SqlCommand(sqlQuery, conn))  
                {  
                    int rowsAffected = command.ExecuteNonQuery(); //execute query and get updated row count  
                    Console.WriteLine(rowsAffected + " row(s) updated");  
                }  
  
                /*FileStream fs = new FileStream(@"C:\Users\Home\source\repos\Test\Test\IP.txt", FileMode.Open, FileAccess.ReadWrite);  
                fs.Seek(0, SeekOrigin.Current);  
  
  
                StreamWriter sw = new StreamWriter(fs);  
                sw.WriteLine(IPAddress);  
  
  
                sw.Close();  
                fs.Close();  
  
                infile = true;*/  
            }  
  
  
            return IPAddress;  
        }  
    }  
   
    class Program  
    {  
        static void Main(string[] args)  
        {  
            GetIP ip = new GetIP();  
            string ipadress = GetIP.GetIPAddress();  
            Console.WriteLine(ipadress);  
            Console.ReadKey(true);  
        }  
    }  
}  

The expectation pops up at :

command.ExecuteNonQuery();  

Any help will be appreciated

Answer 1

The reason for the syntax error is the extraneous trailing comma. If you examine the query in a debugger, it will show a string like INSERT INTO IP (IP) VALUES (N'127.0.0.1', whereas it seems the intended query is INSERT INTO IP (IP) VALUES (N'127.0.0.1'). So you simply need to remove that comma and add a close parenthesis for valid syntax.

There are other serious issues with the code that also need to be addressed. Most importantly, one should never use string concatenation or interpolation to specify SQL statement values. Instead, always use parameters for those values. Below is the corrected version. Note the SQL statement itself never changes, just the parameter value.

string sqlQuery = "INSERT INTO IP (IP) VALUES (@IP);";
using (SqlCommand command = new SqlCommand(sqlQuery, conn))
{
    command.Parameters.Add("@IP", SqlDbType.VarChar, 15).Value = IPAddress;
    command.ExecuteNonQuery(); //execute the Query
    Console.WriteLine("Query Executed.");
}

Another issues is the UPDATE Statement. It has no WHERE clause so every row in the table will be updated. Furthermore, the purpose is not clear since the row with the same value was just inserted. That said, here's an example of a parameterized update query:

string sqlUpdateQuery = "UPDATE IP SET ExampleColumn = @ExampleValue WHERE IP = @IP;";
using (SqlCommand command = new SqlCommand(sqlUpdateQuery, conn))
{
    command.Parameters.Add("@ExampleValue", SqlDbType.DateTime).Value = DateTime.Now;
    command.Parameters.Add("@IP", SqlDbType.VarChar, 15).Value = IPAddress;
    command.ExecuteNonQuery(); //execute the Query
                Console.WriteLine("Query Executed.");
}

It is good you are employing using blocks to ensure objects are immediately disposed. Do the same for the SqlConnection object and other objects that implement IDisposable to avoid leaks.